1. Field of the Invention
The present invention relates to an electromechanical element, an electric circuit device and a method of fabricating the electromechanical element and the electric circuit device.
2. Description of the Related Art
A micro electromechanical element, or MEMS (Micro Electro Mechanical System) is used as a single element for a switch, filter and capacitor or the like, or installed on a common semiconductor substrate with a circuit element of another semiconductor elements or the like to form various electric circuit devices (e.g., see patent publication: Japanese Unexamined patent publication H9-162462).
The MEMS includes a movable element, or an actuator that performs a mechanical vibration or a required mechanical operation of displacement or the like, and is driven by an electrostatic or electromagnetic force or combination of the electrostatic or electromagnetic force or the like. In such MEMS, specifically in surface MEMS, the movable element is usually formed on a sacrifice layer, and a hollowed portion is formed by removing the sacrifice layer located under a movable portion of the movable element, by etching from a circumference of movable portion in a lateral direction, where mechanical operations such as a vibration and displacement can be performed in the hollow.
However, when a perfect hollow is formed under the movable element, later conducting steps of forming electrode, cleaning, drying, inspection of warping and dicing, or the like can be performed on the movable element, mechanical load may be imposed on the movable element. This may cause deformation of or damage to the movable element, thereby resulting in decrease in reliability and production of defective products.
For example, an Al (aluminum) electrode is widely used for an electrode that feeds electricity to the movable element. However, the Al electrode is formed after removing the sacrifice layer by etching since the Al is corroded with a concentrated fluoric acid used as an etching solution for the sacrifice layer. However, forming the Al electrode on the movable element floating in a hollow can impose a comparatively large mechanical load on the movable element, for example, the Al formation of entire surface, an entire surface coating of photoresist for forming a pattern with a required shape, and patterning by photolithography. Such mechanical load on the movable element may cause deformation of or damage to the movable element, which may result in reduction in reliability or production of defective products. Specifically, in a case in which the movable element includes a large area, accurately etching the sacrifice layer that is located under the movable element can be difficult when etching from a circumference to the center of the movable element. Further, since etching may take a long time, etching after the formation of electrode mentioned above may impose some effects on the movable element.